Study on high-K dielectric/regrown nitride semiconductor interfaces for high efficiency and highly-safe transistors

• Project/Area Number: 23K03971
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 21060:Electron device and electronic equipment-related
• Research Institution: University of Fukui
• Principal Investigator: ASUBAR JOEL 福井大学, 学術研究院工学系部門, 准教授 (10574220)
• Co-Investigator(Kenkyū-buntansha): 谷田部 然治 熊本大学, 半導体・デジタル研究教育機構, 准教授 (00621773) ; 葛原 正明 関西学院大学, 工学部, 教授 (20377469)
• Project Period (FY): 2023-04-01 – 2026-03-31
• Project Status: Granted (Fiscal Year 2023)
• Budget Amount: ¥4,680,000 (Direct Cost: ¥3,600,000、Indirect Cost: ¥1,080,000); Fiscal Year 2025: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000); Fiscal Year 2024: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000); Fiscal Year 2023: ¥2,080,000 (Direct Cost: ¥1,600,000、Indirect Cost: ¥480,000)
• Keywords: Normally-off / AlGaN/GaN / HEMT / MIS / Hi-K dielectric / AlGaN / GaN

Outline of Research at the Start

GaNの広いバンドギャップに起因する望ましい物性値により、GaN 系デバイスは、これまでにないパワー、効率、周波数レベルを実現することが可能であり、現代社会で重要な役割を担う。ただし、この優れた2DEGにより、AlGaN/GaN HEMTは、負のしきい値電圧VTHを持つノーマリーオンとなってしまう。つまりゲートに電圧が印加されていない場合でも、電流が端子(ソース-ドレイン)間に流れてしまう。このため、フェイルセーフを確保し、複雑なゲート駆動回路を組み込む必要のない、正のしきい値電圧VTHを備えた「ノーマリーオフ」デバイスの実現が必須である。

Outline of Annual Research Achievements

1) 厚さ 1 nm の AlGaN 再成長の有無を除き、同じ作製プロセスでZrO2/再成長 AlGaN/GaN MIS-HEMT と従来の ZrO2/AlGaN/GaN MIS-HEMT を作製しました。これは、再成長層の挿入によるデバイス性能の向上が何に起因するものかを明らかにする上で重要です。その後のデバイス構造の評価により、目標通りに1 nm の AlGaNが成膜出来ていることが確認出来ました。
2) ZrO2/再成長 AlGaN 界面と従来の ZrO2/AlGaN 界面を調査するために静電容量電圧特性と光支援静電容量電圧特性を測定し両者の比較を行いました。その結果、ZrO2/再成長AlGaNは、従来のZrO2/AlGaN界面に比べて、界面準位が1桁小さいことが明らかになった。測定によるC-V曲線をDIGS(disorder induced gap state)モデルと比較した結果、ほぼ一致していることが確認出来ました。
3) ZrO2/regrown AlGaN/GaN MIS-HEMTと従来のZrO2/AlGaN/GaN MIS-HEMTの電気的特性評価を行った。その結果、厚さ1nmの再成長AlGaN層を挿入することにより、以下の(a)~(c)が確認出来ました。(a)ドレイン電流が1000mA/mmから1050mA/mmに増加(b)ヒステリシスが1.7Vから0.97Vに減少(c)順方向ゲートリーク電流が4桁に減少

Current Status of Research Progress

2: Research has progressed on the whole more than it was originally planned.

Reason

現在、リセス構造を有するZrO2/再成長AlGaN/GaN MISキャパシタおよびリセス構造を有する従来のZrO2/AlGaN/GaN MISキャパシタの比較を行っている。 暫定的な結果の一部を国際学会で報告した。

Strategy for Future Research Activity

来年は以下の研究を予定している。
1. MOCVDチャンバー内におけるNH3およびH2中でのAlGaN表面の成長前工程のアニール条件の最適化。
2. 安定したノーマリーオフ動作を実現するためにしきい値の正のシフトを目的としたZrO2/極薄再成長AlGaN/GaN MISキャパシタの作製と特性評価。
3. ZrO2/極薄再成長AlGaN/GaN構造のキャリア密度、キャリア移動度、散乱機構などの基礎物性の調査。

Research Products

• [Journal Article] Improved Performance of Normally-off GaN-based MIS-HEMTs with Recessed-gate and Ultrathin Regrown AlGaN Barrier (2024)
  • Author(s): Shogo Maeda, Shinsaku Kawabata, Itsuki Nagase, Ali Baratov, Masaki Ishiguro, Toi Nezu, Takahiro Igarashi, Kishi Sekiyama, Keito Shinohara, Melvin John F. Empizo, Nobuhiko Sarukura, Masaaki Kuzuhara, Akio Yamamoto, and Joel T. Asubar
  • Journal Title: Journal of Semiconductor Technology and Science Volume: 24 Issue: 1 Pages: 25-32
  • DOI: 10.5573/jsts.2024.24.1.25
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Effect of Ultra-Thin AlGaN Regrown Layer on the Electrical Properties of ZrO2/AlGaN/GaN Structures (2024)
  • Author(s): Toi Nezu, Shogo Maeda, Ali Baratov, Suguru Terai, Kishi Sekiyama, Itsuki Nagase, Masaaki Kuzuhara, Akio Yamamoto, and Joel T. Asubar
  • Journal Title: Phys. Status Solidi A Volume: 2024 Issue: 21
  • DOI: 10.1002/pssa.202400073
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Low thermal budget V/Al/Mo/Au ohmic contacts for improved performance of AlGaN/GaN MIS-HEMTs (2023)
  • Author(s): Ali Baratov, Takahiro Igarashi, Masaki Ishiguro, Shogo Maeda, Terai Suguru, Masaaki Kuzuhara, Joel T Asubar
  • Journal Title: Japanese Journal of Applied Physic Volume: 62 Issue: 11 Pages: 110905-110905
  • DOI: 10.35848/1347-4065/ad057a
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] High performance normally-off recessed-gate GaN-based MIS-HEMTs achieved by oxygen plasma treatment (2023)
  • Author(s): M Ishiguro, S Terai, K Sekiyama, S Urano, A Baratov, JT Asubar, M Kuzuhara
  • Journal Title: 2023 IEEE IMFEDK Tech. Dig. Volume: 2023 Pages: 1-2
  • DOI: 10.1109/imfedk60983.2023.10366337
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] AlGaN/GaN Schottky-Gate HEMTs with low thermal budget V/Al/Mo/Au ohmic contacts (2023)
  • Author(s): T Igarashi, S Maeda, A Baratov, JT Asubar, M Kuzuhara
  • Journal Title: 2023 IEEE IMFEDK Tech. Dig. Volume: 2023 Pages: 1-2
  • DOI: 10.1109/imfedk60983.2023.10366331
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] MOVPE growth of AlGaN on RIE-treated GaN surfaces and its application to AlGaN/GaN electron devices (INVITED) (2023)
  • Author(s): Akio Yamamoto, Ali Baratov, Masaaki Kuzuhara, and Joel T Asubar
  • Journal Title: 2023 IEEE IMFEDK Tech. Dig. Volume: 2023 Pages: 1-5
  • DOI: 10.1109/imfedk60983.2023.10366345
  • Peer Reviewed / Int'l Joint Research
• [Presentation] Interface characterization of regrown-AlGaN/ZrO2 interfaces for Normally-off GaN-based MIS-HEMTs (2024)
  • Author(s): Joel T. Asubar, Itsuki Nagase, Ali Baratov, Masaki Ishiguro, Shogo Maeda, Toi Nezu, Takahiro Igarashi, Kishi Sekiyama, Suguru Terai, Masaaki Kuzuhara, and Akio Yamamoto
  • Organizer: WOCSDICE-EXMATEC 2024, Crete, Greece
  • Int'l Joint Research
• [Presentation] Innovation Technologies for Highly Safe and Energy-efficient GaN Devices (invited talk) (2023)
  • Author(s): Joel T. Asubar
  • Organizer: IEEE R10 Webinar Series IEEE R10 Talk
  • Int'l Joint Research / Invited
• [Presentation] Threshold voltage control in GaN-based MIS-HEMTs with recessed structure and regrown AlGaN barrier layers (2023)
  • Author(s): Joel T. Asubar, Shinsaku Kawabata, Shun Urano, Itsuki Nagase, Ali Baratov, Masaki Ishiguro, Shogo Maeda, Toi Nezu, Takahiro Igarashi, Kishi Sekiyama, Masaaki Kuzuhara, and Akio Yamamoto
  • Organizer: WOCSDICE-EXMATEC 2023, Palermo (Italy)
  • Int'l Joint Research
• [Presentation] Improved Performance of Normally-off GaNbased MIS-HEMTs with recessed-gate and ultrathin regrown AlGaN barrier (2023)
  • Author(s): Shogo Maeda, Shinsaku Kawabata, Itsuki Nagase, Ali Baratov, Masaki Ishiguro, Toi Nezu, Takahiro Igarashi, Kishi Sekiyama, Keito Shinohara, Melvin John F. Empizo, Nobuhiko Sarukura, Masaaki Kuzuhara, Akio Yamamoto, and Joel T. Asubar
  • Organizer: 2023 Asia-Pacific Workshop on Advanced Semiconductor Devices (AWAD 2023)
  • Int'l Joint Research
• [Presentation] Effects of low thermal budget V/Al/Mo/Au ohmic contacts on the performance of AlGaN/GaN MIS-HEMTs (2023)
  • Author(s): Ali Baratov, Takahiro Igarashi, Masaki Ishiguro, Shogo Maeda, Masaaki Kuzuhara, and Joel T. Asubar
  • Organizer: 2023 Asia-Pacific Workshop on Advanced Semiconductor Devices (AWAD 2023)
  • Int'l Joint Research
• [Presentation] GaN-based MOS-HEMTs with Mist Chemical Vapor Deposited Insulator (2023)
  • Author(s): K. Bito, H. Hiroshige, R. Hashimoto, M. Ishiguro, J. T. Asubar, Y. Nakamura, and Z. Yatabe
  • Organizer: 14th international Conference on Nitride Semiconductors (ICNS 14)
  • Int'l Joint Research
• [Presentation] Effect of ultra-thin AlGaN regrown layer on the electrical properties of ZrO2/AlGaN/GaN heterostructures (2023)
  • Author(s): T. Nezu, S. Maeda, A. Baratov, I. Nagase, K. Sekiyama, S. Terai, M. Kuzuhara, A. Yamamoto, and J. T. Asubar
  • Organizer: 14th international Conference on Nitride Semiconductors (ICNS 14)
  • Int'l Joint Research
• [Presentation] Comparative studies of electron state distribution in Al2O3/AlGaN/GaN and ZrO2/AlGaN/GaN structures (2023)
  • Author(s): Nur Syazwani B. A. T., S. Maeda, A. Baratov, J. T. Asubar and M. Kuzuhara
  • Organizer: 2023 IEEE International Meeting for Future of Electron Devices ,Kansai (IMFEDK 2023)
  • Int'l Joint Research
• [Presentation] AlGaN/GaN Schottky-Gate HEMTs with low thermal budget V/Al/Mo/Au ohmic contacts (2023)
  • Author(s): T. Igarashi, S. Maeda, A. Baratov, J. T. Asubar and M. Kuzuhara
  • Organizer: 2023 IEEE International Meeting for Future of Electron Devices ,Kansai (IMFEDK 2023)
  • Int'l Joint Research
• [Presentation] High performance normally-off recessed gate GaN-based MIS-HEMTs with oxygen plasma treatment (2023)
  • Author(s): M. Ishiguro, K. Sekiyama, S. Urano, A. Baratov, J. T. Asubar and M. Kuzuhara
  • Organizer: 2023 IEEE International Meeting for Future of Electron Devices ,Kansai (IMFEDK 2023)
  • Int'l Joint Research
• [Presentation] MOVPE growth of AlGaN on RIE-treated GaN surfaces and its application to AlGaN/GaN electron devices (INVITED) (2023)
  • Author(s): Akio Yamamoto, Ali Baratov, Masaaki Kuzuhara, and Joel T. Asubar
  • Organizer: 2023 IEEE International Meeting for Future of Electron Devices ,Kansai (IMFEDK 2023)
  • Int'l Joint Research
• [Presentation] Cu/Al/Mo/Au電極を用いたGaN系デバイスにおけるRTA温度と電気的特性の関係 (2023)
  • Author(s): Kensei Sumida, Ali Baratov, Shogo Maeda, Terai Suguru, Masaaki Kuzuhara, Joel T. Asubar
  • Organizer: 令和5年度応用物理学会 北陸・信越支部学術講演会
• [Presentation] ZrO2/Al2O3多層nano‐laminate絶縁体を有するAlGaN/GaN MIS‐HEMTsと従来のAl2O3およびZrO2 AlGaN/GaN MIS‐HEMTsの電気的特性の比較 (2023)
  • Author(s): Suguru Terai, Ali Baratov, Shogo Maeda, Masaki Ishiguro, Masaaki Kuzuhara, Joel T. Asubar
  • Organizer: 令和5年度応用物理学会 北陸・信越支部学術講演会
• [Remarks] University of Fukui Electron Device Laboratory
  • URL: https://sites.google.com/view/uf-electron-device-lab/home-%E3%83%9B%E3%83%BC%E3%83%A0
• [Remarks] Google Scholar
  • URL: https://scholar.google.com/citations?hl=en&user=1NlRAggAAAAJ
• [Remarks] Researchgate
  • URL: https://www.researchgate.net/profile/Joel-Asubar